The present invention relates to a nozzle assembly for applying a liquid to a substrate.
In many fields of application, especially those for producing wafers and masks during the treatment of a substrate, it is necessary to deposit a layer of liquid such as a developer for example, on the wafer or the mask.
In the past, this has been done using a single nozzle which was directed towards the substrate and was swept or scanned over the mask or the wafer in raster-like manner in order to wet the entire surface of the substrate. As an alternative, consideration has also been given to the use of several mutually adjacent nozzles which were directed towards the surface of the substrate and wetted the entire substrate in the course of a single sweep.
If the liquid being applied is, for example, a liquid developer which is used for the development steps in a micro-lithographic process, it is important for the quality of the final product to ensure that the same process progress is reached—i.e. that there is a uniform degree of development—over each sub-area of the surface of the substrate being treated. The rate at which the process progresses is basically determined by the quantity of developer applied, the dwell time on the substrate and the mechanical force with which the liquid is applied to the surface of the substrate. Consequently, it is necessary for the developer to be applied simultaneously over the entire surface of the substrate in as force-free and homogeneous a manner as possible in order to ensure that the process progresses at as homogeneous a rate as possible.
In order to ensure that the liquid is applied as simultaneously as possible when applying it through a single nozzle, the nozzle should have a very high scanning speed, and a very high flow speed for the medium should be selected since large temporal inhomogeneities in the application of the medium would otherwise arise. However, the high speed of flow leads to a large mechanical deposition force during the application of the medium, this being something which should be avoided. Moreover, when using a single nozzle, a pattern corresponding to the pattern of the nozzle develops on the surface of the substrate because the medium is not usually applied evenly over the width of the area being supplied by the nozzle—both in regard to the force of application and the quantity of liquid applied.
When using a plurality of mutually adjacent nozzles, the application time can be substantially reduced as compared with a single nozzle, whereby the temporal inhomogeneity can be reduced when the medium is applied in this manner. However, it is still necessary to use high speeds of flow in order to enable the medium to be applied as simultaneously as possible, this thereby again resulting in a large mechanical deposition force during the application of the medium. Moreover, the development of a pattern described above still occurs for the individual nozzles.
Furthermore, a slot nozzle for applying a liquid high-polymer material is known from EP 03 66 962 A2. The slot nozzle consists of a two-piece nozzle body, whereby a first part incorporates a feed channel and several stop valves which are able to open and close a connection between the feed channel and corresponding outlet bores in the first part. Each of the outlet bores extends towards the second part of the nozzle body and is directed towards an elongated spreading chamber which is in the form of a recess in the second part. An outlet slot is formed between the two parts below the spreading chamber.
Based upon the above state of the art, the object of the present invention is to provide a device which enables rapid, homogeneous application of a liquid to a substrate in as force-free a manner as possible.